At

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Returns the value at the specified key in the current Vector

public function at(
  int $key,
): Tv;

If the key is not present, an exception is thrown. If you don't want an exception to be thrown, use get() instead.

$v = $vec->at($k) is semantically equivalent to $v = $vec[$k].

Parameters

• int $key

Returns

• Tv - The value at the specified key; or an exception if the key does not exist.

Examples

This example prints the first and last values of the Vector:

$v = Vector {'red', 'green', 'blue', 'yellow'};

// Print the first element
\var_dump($v->at(0));

// Print the last element
\var_dump($v->at(3));

This example throws an OutOfBoundsException because the Vector has no index 10:

$v = Vector {'red', 'green', 'blue', 'yellow'};

// Index 10 doesn't exist (this will throw an exception)
\var_dump($v->at(10));